Thermoplastic polyester resins, such as poly-butylene terephthalate and poly-ethylene terephthalate, or polyacetal resins have been used in a number of end-use applications as engineering resins in recent years since they exhibit superior mechanical and electrical properties, heat and, chemical resistances, and workability. And, there is a tendency that these resins will be used under still more severe conditions with an expansion of their end-use applications. As such, these resins are required to exhibit improved properties for many such end-use applications. Some of these properties are an improved frictional characteristic, long-term durability of the improved frictional characteristics, a reduction of frictional noise due to the sliding or the like of a part formed of such resins, such as sliding members and mechanism members for cars, electric and electronic products and the like.
For example, it is known that (1) solid lubricants, such as molybdenum disulfide and graphite, (2) powdery and fibrous poly-tetrafluoroethylene resin (3) liquid or semi-solid lubricants, such as petroleum lubricating oils, synthetic lubricating oils, aliphatic alcohols or their esters, are added; and the like may be added as a means of improving the frictional and abrasive characteristics of thermoplastic resins. It goes without saying that some improvements in the frictional and abrasive characteristics by these known methods ensue and in particular the requirements can be met in those situations where a part formed of such resins is used only for a short time under sliding conditions at relatively slow speeds and loads. However, problems have occurred in that the frictional characteristics become insufficient as the sliding speed and load increase. The frictional characteristics therefore significantly deteriorate over time in use even under sliding conditions at low speeds and loads. In addition, it is known that polyethylene, polytetrafluoroethylene and the like may be added to soften resins, and has been generally used as a method of improving frictional noise when sliding. However, with this known technique, a silencing property capable of meeting the requirements cannot always be attained. In addition, problems have occurred in that physical properties, such as mechanical strength, decrease.
As above described, according to the conventional known techniques, the requirements, which are being increasingly made more severe, cannot be met with respect to frictional and abrasive characteristics, in particular characteristic under high speed and high sliding conditions or in terms of load, long-term anti-friction or silencing characteristics when sliding. Accordingly, improvement in these areas has been needed.